Design Of Electrochemical Pump Functional Unit And Study On Preparation Process Of NO_x Sensor

With the increase of vehicle ownership,the environmental pollution caused by NO_X emission is becoming more and more serious.Therefore,more stringent standards for vehicle exhaust emission have been formulated in various countries.As the core component of SCR control system,NO_X sensor chip is complex in technology and difficult to fabricate.However,the domestic NO_X sensor chip has the problems of low yield and low measurement accuracy and now it mainly depends on imports.In order to adapt to the new standards,it is urgent to develop a more accurate domestic NO_X sensor.This paper focuses on improving chip testing accuracy and process improvement.The response of chip made by myself and NGK chip were tested by a self-made signal testing system that could simulate automobile exhaust air.The working principle of the chip and stability of the system were verified.The preparation of diffusion barrier layer and the co-firing of alumina and zirconia tape sheets at high temperature were studied by screen printing and tape casting.A signal test system for simulating the automobile exhaust environment was designed and the circuit control strategy of the chip was improved.By testing the NGK chip,the results showed that the signal of the test system was stable and accurate,and the diffusion resistance of the three pumps was calculated.The constant current control strategy could reduce the compensation current and improve the test accuracy.The response characteristics of the chip measurement pump to the diffusion barrier layer with LSM were studied.Results showed that adding LSM to the diffusion barrier could improve the limit current platform of the measurement pump,effectively reduce the diffusion resistance of the diffusion barrier,and improve the measurement accuracy and range of the measurement pump.Adding 6wt%LSM powders to the diffusion barrier,a good linear relationship between the concentration of O₂ and current Ip₂ was obtained.The high temperature co-firing matching of alumina and zirconia cast sheets was studied.The results showed that the sintering shrinkage of the cast sheet was related to the alumina particle size and the content of the cast rubber.The smaller the particle size,the larger the shrinkage rate,and the cast rubber content was positively correlated with the sintering shrinkage rate.The co-sintering effect of alumina and zirconia could be strengthened by adding 1%toluene+99%ethanol and tape adhesive to the surface treatment,compact sintering state could be obtained by isostatic pressing,and the best co-sintering effect could be obtained by co-sintering alumina tape and zirconia with 8%5YSZ powder.